Characterization of Macro and Micronutrients Associated With the Root Zone of Cactaceae Species From Xerophytic Forests

The soil of the root zone plays a crucial role in plant physiology. In this study, we analyzed the chemical properties of root zone soils from cacti occurring in karstic, crystalline, and sedimentary areas within xerophytic forests of the Caatinga domain and the Cerrado–Caatinga ecotones in eastern Brazil. Soil samples were analyzed for macro- and micronutrient profiles, pH, and fertility metrics. Principal components (PCA), linear discriminant (LDA), random forest (RF), and support vector machine (SVM) analyses were applied to distinguish soil types. Our results indicated that the karstic root zone soil around cacti had higher pH, fertility, and specific nutrient concentrations compared to crystalline and sedimentary root zone soils. The RF and SVM approaches demonstrated superior discrimination capabilities compared to LDA, with SVM achieving 95.31% correct reclassification. Organic material, calcium, and potassium were the main predictors of root zone soil reclassification for each terrain. These findings reveal the edaphic diversity of Caatinga soils and their role in shaping cactus communities, providing insights into the ecological and evolutionary dynamics of these xerophytic plants. We emphasize the significance of soil characteristics in biogeographic investigations and present potential implications for explaining biome shifts and historical corridors between adjacent biomes.